The present invention relates to a golf club group in which a plurality of golf clubs of the same number are categorized by a swing type, one of golf clubs constituting the golf club group and a fiber reinforced resin golf club shaft constituting the golf club.
In general, golfers are broadly categorized by his swing characteristics into the two following types. One type of golfer is a so-called "swinger" who swings a golf club while bending a golf club shaft 12 by turning his wrist 11 from the beginning of swing A so that a club head 13 describes a relatively large approximately circular arc X around a swing center O, as shown in FIG. 7.
Another type of golfer is a so-called "hitter" who swings the golf club without turning his wrist 11 at the beginning of swing so that the club head 13 describes a relatively small approximately circular arc Y around the swing center 0 and then accelerates a head speed while sharply turning his wrist at the time of impact J, as shown in FIG. 8.
Heretofore, as a criterion for thus categorizing golf clubs in a manner suitable for the swing characteristics, the flexibility and bend point indicating flexural rigidity properties of the whole golf club shaft have been used. The golf clubs are categorized in the following manner, for example. The golf club having the golf club shaft of high flexibility, that is, the golf club with a relatively soft shaft, is suitable for the swinger, while the golf club having the golf club shaft of low flexibility, that is, the golf club with a relatively hard shaft, is suitable for the hitter. Alternatively, the golf club having the golf club shaft whose bend point is closer to a tip end and which is of low flexural rigidity near the tip end is suitable for the swinger, while the golf club having the golf club shaft whose bend point is closer to a butt end and which is of high flexural rigidity near the tip end is suitable for the hitter.
In the case of selling the same brand of golf club group including two kinds or more of golf clubs which are of the same number and of different properties of the golf club shafts, golf club makers mark the golf clubs with characters, patterns or the like so as to thereby categorize the golf clubs in such a manner that the swinger or the hitter can be easily select the suitable golf club from this golf club group in accordance with his own characteristics.
However, since a method of categorizing the golf clubs by the use of the above-described flexibility and bend point is not the categorizing method in which the swinger and the hitter can sufficiently hit a ball in their ways, the above-mentioned method is not necessarily satisfactory.
That is, the method of categorizing the golf clubs by means of the flexibility and bend point is accomplished by categorizing the golf club having the shaft of characteristics considered to be physically appropriate on the basis of the characteristics of swing speed and trajectory in terms of the swing speed estimated from the characteristics of swing type and the experientially known characteristics of trajectory. This categorizing method does not take golfer's sensitivity into consideration, and it does not analyze/consider shaft deformation in a swing process.